The Study Of Optical And Electrical Properties On ZnO And Ga Doped ZnO Nanopowders

Today,nano-materials are most vibrant study object in the areas of new materials' research and will have an important impact in the future economic and social development.Simultaneously,nano-materials are the most active in nanotechnology and an important part of the closest application.Nano-materials have a lot of special performance,such as quantum size effect,small size effect and surface effect,which have a major impact on low-dimensional nanomaterials,such as the transport and optical properties.At the same time,the low-dimensional nano-materials system has more advantageous electrical,optical,magnetic and mechanical properties than bulk materials.In recent years,the research of nano-materials and its performance has made tremendous progress,however,there are still a lot of problems to be solved,but also full of opportunities.Zinc oxide(ZnO) is a direct wide bandgap semiconductor material ofâ…¡-â…¥group with band gap 3.37eV at room temperature and exciton binding energy 60meV.ZnO has been widely applied in the field of the transparent semiconductor,light-emitting devices, solar cell window material,waveguide,monochrome field emission display, high-frequency piezoelectric transducer,surface acoustic wave components, micro-sensors as well as the low-voltage piezoelectric resistors due to its excellent piezoelectric properties,photoelectric properties,pressure-sensitive properties and gas sensing properties.ZnO nano-materials have attracted much interest from domestic and international scientific community and industrial department because they have both the special properties of nano-material and the advantages of semiconductor.At present,the research of ZnO optical,electric properties is universally concerned.In order to enhance ZnO optical,electrical properties,an effective method is to dope another Material in ZnO.Now,many research groups focus on the study of doped ZnO nanomaterials for improving its optical and electrical properties.Recently,the preparation method and performance of ZnO,Ga doping ZnO was often reported,but these studies mainly focused on the thin film.The optical,electrical properties of ZnO,Ga-doped ZnO nano-powders are reported less.Therefore,it is very significant for basic research to study systematically the optical,electrical properties of ZnO,Ga-doped ZnO nano-powders.In this paper,we focused on the research of the synthesis and optical,electrical properties of ZnO,Ga-doped ZnO nano-powders.This will provide a theoretical basis and experimental foundation for ZnO materials better and more widely used.As follows:(1) A large number of different morphology ZnO single crystals with hexagonal wurtzite structure were synthesized by hydrothermal/solvothermal combined with the precipitation method.And the optical properties of these ZnO samples were systematically study.The research results show infrared absorption of samples blue shift because of the impact of quantum size effect.And the blue shift was also related to the size of the particle.For the small size particle(diameter＜300nm),blue shift is obviously larger than those sub-micro particles.In addition,from the UV-vis absorption spectra,it was found there are 2-3 new absorption peaks when the sample's diameter was less than 300nm.Some new peaks can be split from the bulk peak.In our study,the spindly nanorods have the best absorption in visible region,which has strong absorption at almost the entire visible light region.But the nanorods with the large aspect ratio(＞15) had strong absorption only in UV region.There is almost no absorption in visible region.According to PL spectra,the emission peak of ZnO samples(diameter＜300nm) appeared 399nm and 466nm nearby.We speculated the two emission peaks can be the small size ZnO nanopowders' characteristic peaks of PL spectra.(2) Ga-doped ZnO nanopowders with wurtzite structure were obtained from the zinc precursor solutions with different Ga concentration via a simple solvothermal route. The structural,optical and electrical properties of the as-obtained nanopowders have been investigated in detail.The effect of different Ga concentration in precursor solution on the sample morphology,optical absorption,fluorescence and electrical properties were discussed.The research results show the morphology of the as-obtained nanopowders changed from rod-like to spherical or short hexagonal prism, simultaneously,the size of the corresponding nanoparticles reduced gradually by increasing the mole ratio of Ga to Zn from 0 to 5%in zinc precursor solutions.And the crystalline state also altered from single crystal to multicrystal.PL spectra of the Ga-doped ZnO nanopowders reveal that the near band emission(NBE) peak gradually red-shift with Ga concentrations in zinc precursor solutions increased from 0 to 5 mol% due to band renormalization effect.The UV-vis absorption spectra disclosed that the Ga doping caused the absorption band broaden,which makes the as-prepared Ga-doped ZnO samples have strong absorption in the whole visible region.Electrical characteristics analysis show,for 0,1,2 and 5 mol%Ga,the carrier concentration increased,the resistivity and electron mobility decreased with Ga concentration increasing.The optimal electrical properties of ZnO:Ga-NPs in the study are carrier concentration of 6.20×10¹⁵ cm^-3 and resistivity of 0.234Ωm.This provides a potential application in enhancing the electrical characteristics of organic compound by embedding the ZnO:Ga-NPs into the organic compound.